usage of chalk

In prehistoric times, chalk was used by ancient people to draw and paint in the caves as a religion and/or cultural practice.

Chalk is even used in toothpaste and it is after water in quantity.

Some people use it to dye their hair.

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How does chalk work?

Chalk is very powdery so how it works is that when one rubs it against chalkboard, it gets off the stick of chalk and comes on to the board. Then, it stays on the board because water is added to it during the manufacturing process. Similarly, chalk also stays on sidewalks and in cave walls. But when you rub it with foam, or a cloth, the powder comes off the board or the sidewalk.